1. Field of the Invention
The present invention relates to the field of vision systems, and more particularly, to vision systems for the quantitative evaluation of an area, surface and/or the size, shape or orientation of an outline or a portion thereof.
2. Prior Art
In recent years considerable effort has been expended in developing methods and apparatus for the automatic inspection and/or quantitative evaluation of various manufactured or other things, as automatic inspection in most instances offers the possibility of substantially reducing labor costs, of eliminating human error, frequently aggravated by the monotony of many inspection tasks, and of providing greater uniformity in the inspection or evaluation results. Of particular importance to some applications of the present invention are those applications which require the evaluation of an area, and more particularly of a bounded area wherein the area is intended to be evaluated right up to the boundaries thereof, or alternatively, the location of and/or characteristics determined by the boundary (position orientation, etc. of the item).
By way of example, in some instances, such as in medical specimen analysis, a portion of an area or image is to be analyzed as representative of the entire specimen In such instances the surface being inspected or analyzed is physically larger than the portion thereof used for vision system analysis so that the edges of the image analyzed are in effect data boundaries, not object boundaries In other instances however, such as in the automatic inspection of parts in a manufacturing environment, one normally desires to inspect the surface of the part right up to the edges of the image thereof. Using light intensity gradient analysis of the image results in a very strong emphasis of the image boundaries, which in effect must be eliminated before the remaining data will be useful This can be done by finding a boundary in the data and then erasing the data corresponding to the edge by use of an algorithm which effectively bounces back and forth across the edge to isolate the data to be erased. It can also be done by scanning the object to threshold it with its background to detect and erase the edges, though both of these techniques are time consuming and generally require knowledge of the shape of the object, and if not fundamentally round, of its orientation also. While a fixed digital mask could be used to mask the image once stored in memory in digital form, such a technique would require very accurate position and orientation of the object, frequently not feasible in a real time, high speed inspection environment.
Image analysis hardware and analytical techniques which depend upon the intensity gradient across the image area do effectively distinguish regions of an area which for any reason have a light intensity which begins to deviate from the intensity of surrounding areas. In effect, the intensity gradient is the first derivative of intensity itself, which results in the emphasis of point to point changes regardless of their causes. The purpose of the present invention is to provide a method and apparatus for automatic inspection which will automatically detect, and if desired, emphasize or de-emphasize part boundaries, and which will readily facilitate data smoothing, shaping and other manipulation to result in a very high speed and reliable inspection system. As an example of a present invention system which in effect is used to de-emphasize part boundaries, an inspection system is described herein for inspecting O-rings for surface defects therein. In general, O-rings have not been inspected by prior art inspection systems because of the prominence of the ID and OD boundaries thereof, particularly in comparison to the relatively limited surface area of typical O-rings, and the flexibility of at least many O-rings, making the very accurate positioning of an O-ring so that the edges thereof may be masked within the system substantially impossible. Another example of the application of the present invention disclosed herein is the inspection of beans and the like to detect the presence of one or more stems thereon. In this case the present invention is used to emphasize the stem boundaries, with the presence of the stem being detected by detecting the presence of an image portion having adjacent edge boundaries of a separation indicative of the presence of the stem. In general, prior art inspection systems have not been able to detect the presence of stems on such food products, as the lack of orientation of the items being inspected, together with the lack of ability of prior art techniques to uniquely characterize stems no matter where located in the field of view, has left prior art techniques substantially useless for such applications. These of course are but mere examples of the ability of the present invention system to be tailored to work satisfactorily in various applications in which prior art techniques are not useful, merely by making various adjustments and parameter changes in the system and/or the manner in which the final data is analyzed and/or combined to highlight the effect being inspected for.